President Barack Obama works on his speech to the American Israel Public Affairs Committee (AIPAC) with Ben Rhodes, Deputy National Security Advisor for Strategic Communications, in the Oval Office, Saturday, March, 3, 2012. (Photo by Pete Souza)

Throughout Black History Month, I’ve included tweets in ‘A Tweet Or Two’ about African-American heroes who with brains, love, strength, blood, sweat, tears, and death; built this nation to what it is today. As Black History Month draws to a close, we celebrate the known and unsung heroes who gave everything and continue to give everything to make this country live up to its promise of “all men are created equal.”

AFTUnion: 13 Labor Events And Organizers Who We Should Teach About During Black History Month

Lucy Parsons was a radical labor organizer born in Texas. In the early 1870s, she and her husband had to flee Texas because of intolerant reactions to their interracial marriage. Throughout her subsequent career in Chicago, she wrote for various leftist and labor publications. In 1905, she participated in the founding of the Industrial Workers of the World. In 2004, the city of Chicago named a park after her.

Randolph is one of the most important figures in both black history and labor history. In addition to his work with the Pullman porters (see No. 2, above) and the 1963 March on Washington for Jobs and Freedom, he prominently pushed for civil rights during World War II. He planned a 100,000 person march on Washington during the war, which led President Franklin D. Roosevelt to sign an executive order ending discrimination in defense industries. After the order was signed, the march was canceled.

In the late 1860s, George Pullman hired former slaves to work on his railroad sleeping cars. He exploited their labor, with each porter making the equivalent of about $22,000 a year (in today’s dollars) while working under unfair conditions, including 100-hour workweeks. These workers formed a union, the Brotherhood of Sleeping Car Porters; in 1925, it became the first African-American labor union to receive a charter in the American Federation of Labor.

Rosina Tucker was an important figure in the foundation of the Brotherhood of Sleeping Car Porters. Tucker was married to a railroad porter and became involved in the union. She visited the homes of over 300 workers to secretly collect their union dues, and in 1938 she was elected secretary-treasurer of the union’s auxiliary. She continued her union involvement, helping organize teachers, laundry workers and railway clerks in Washington, D.C.

In the 1920s, the Chicago Flat Janitors were an integrated local union, which was considered radical at the time. The union worked to include black members in leadership roles, including its vice president, Seymour Miller. The union eventually grew and today is known as the Service Employees International Union, or SEIU.

President Obama on Tuesday vetoed a bill to approve construction of the Keystone XL oil pipeline, rejecting an effort by Republicans and some Democrats to force his administration to let the highly contested energy project move forward. By saying no to the legislation, Mr. Obama retains the authority to make a final judgment on the pipeline on his own timeline. The White House has said the president would decide whether to allow the pipeline when all of the environmental and regulatory reviews are complete. But the veto — his first rejection of major legislation as president — is also a demonstration of political strength directed at Republicans who now control both chambers of Congress.

Mr. Obama is signaling that he will fight back against their agenda. The Obama administration must decide whether to approve infrastructure projects like the Keystone pipeline, which cross a border with another country. In his veto message to Congress, delivered with no fanfare on Tuesday afternoon, Mr. Obama wrote that the legislation “attempts to circumvent longstanding and proven processes for determining whether or not building and operating a cross-border pipeline serves the national interest.” Mr. Obama added that “because this act of Congress conflicts with established executive branch procedures and cuts short thorough consideration of issues that could bear on our national interest — including our security, safety, and environment — it has earned my veto.”